Structural health monitoring of the Roman Arena of Verona, Italy

Ancient structures, especially very old ones, prove their soundness and the correctness of their structural layout by reaching our days in good conditions. This is the case of the Roman Arena in Verona—Italy, built in the first century A.D., and still standing in the historical centre of Verona. It became certainly the symbol of the city and it is open to public use for visits and also for operas, concerts and relevant shows. However, with a closer look, it is possible to appraise damages that the passing of time and the natural or man-induced events such as historical earthquakes and floods or wars and sieges left on the structure. Seismic events (the worst ones recorded in 1116, 1117 and in 1183) induced serious damages on the Arena since they caused the almost complete collapse of the third external ring of the monument, today only remaining in the so-called ‘‘wing’’ of the Arena, a freestanding curved wall composed by huge blocks of stone and characterized by a repetition of arches and massive pillars. With the purpose of evaluating the structural response of the Arena to static, dynamic (e.g. shows, concerts) and seismic loads, a structural health monitoring (SHM) system was installed in 2011, with a state-of-the-art technology to record meaningful data through a sensors’ network installed in relevant positions of the monument. A detailed crack pattern survey was carried out to identify main cracks and damages and select the most suitable positions for static sensors, able to control the reversibility of the seasonal displacements or deformations trends of the monument. Ambient vibration tests were also carried out to extract the fundamental modal parameters and calibrate/update reference finite elements models: global modes were identified and—with a special focus on the wing—acceleration sensors were installed in the areas where significant dynamic amplifications are expected according to the numerical simulation. The paper reports the preliminary activities carried out before the installation of the SHM system and illustrates the results of the first 1.5 year of monitoring analysing both the operational conditions of the structure and its response in case of exceptional events. Specific algorithms were developed and implemented to perform the continuous real-time treatment of static data and the automated identification of modal parameters.